Evaluation at industrial scale of electric-driven heat pump dryers (HPD)

Abstract

Electric-driven heat pump drying is evaluated in lumber from different softwoods (Maritime, radiata and Scot pines) and hardwoods (Iroko, Beech). The evaluation was carried out at industrial scale being controlled by five different driers over a two-year period. Up to 235 different cycles of drying were evaluated. Specific energy consumption seems to be between 0.64 kWh/l to 0.73 kWh/l in softwoods and between 1.0 to 1.3 kWh/l in hardwoods. These values are much lower than those usually reported for the traditional kiln drying. In moderate permeable lumber, the overall duration of drying is very similar to traditional kiln drying, but is longer in the case of very permeable softwoods. This drying technology seems to be efficient when drying lumber, at least when medium temperatures (65–70°C) are involved.